1. Field of the Invention
The present invention relates to a bearing support structure for an actuator, for supporting a bearing arranged at a sliding portion between a main actuator body and an actuator displacement member.
2. Description of the Related Art
An actuator such as a rodless cylinder has been used as a means for transporting a workpiece. For example, the rodless cylinder includes a guide rail, which is formed in the axial direction of a cylinder body. A displacement member is provided, which is displaced with respect to the guide rail. A slide member, which functions as a bearing, is arranged between the displacement member and the guide rail. A projection, which protrudes toward the displacement member, is formed at one end of the slide member. The projection engages with an indented recess of the displacement member. In this structure, when the displacement member is displaced, the displacement member and the slide member are displaced together in an integrated manner in the axial direction. Accordingly, the slide member reduces sliding resistance between the displacement member and the guide rail (see, for example, Japanese Laid-Open Patent Publication No. 2004-522099 (PCT)).
In the case of the actuator described in Japanese Laid-Open Patent Publication No. 2004-522099 (PCT), when the displacement member is displaced along the guide rail, a displacement force of the displacement member is applied to the projection of the slide member, and the projection is pressed in the axial direction while the displacement member is displaced. Accordingly, the slide member and the displacement member are displaced in an integrated manner. However, when the displacement member is displaced, sliding resistance in a direction opposite to the displacement direction of the displacement member is generated between the guide rail and the sliding surface of the slide member, which abuts against the guide rail.
In particular, a displacement force which generates a compressive stress depending on the operating direction of the displacement member, and a displacement force which applies a tensile stress, exist between the projection of the slide member and the sliding surface. Therefore, an alternating load is applied between the projection and the sliding surface, and thus the durability of the slide member deteriorates due to the alternating load.